<?php

/* SVN FILE: $Id$ */
/**
 * SassVariableNode class file.
 * @author      Chris Yates <chris.l.yates@gmail.com>
 * @copyright   Copyright (c) 2010 PBM Web Development
 * @license      http://phamlp.googlecode.com/files/license.txt
 * @package      PHamlP
 * @subpackage  Sass.tree
 */

/**
 * SassVariableNode class.
 * Represents a variable.
 * @package      PHamlP
 * @subpackage  Sass.tree
 */
class SassVariableNode extends SassNode
{

    const MATCH = '/^([!$])([\w-]+)\s*:?\s*((\|\|)?=)?\s*(.+?)\s*(!default)?;?$/i';
    const IDENTIFIER = 1;
    const NAME = 2;
    const SASS_ASSIGNMENT = 3;
    const SASS_DEFAULT = 4;
    const VALUE = 5;
    const SCSS_DEFAULT = 6;
    const SASS_IDENTIFIER = '!';
    const SCSS_IDENTIFIER = '$';

    /**
     * @var string name of the variable
     */
    private $name;

    /**
     * @var string value of the variable or expression to evaluate
     */
    private $value;

    /**
     * @var boolean whether the variable is optionally assigned
     */
    private $isDefault;

    /**
     * SassVariableNode constructor.
     * @param object source token
     * @return SassVariableNode
     */
    public function __construct($token)
    {
        parent::__construct($token);
        preg_match(self::MATCH, $token->source, $matches);
        if (empty($matches[self::NAME]) || ($matches[self::VALUE] === '')) {
            throw new SassVariableNodeException('Invalid variable definition; name and expression required', $this);
        }

        $this->name = $matches[self::NAME];
        $this->value = $matches[self::VALUE];
        $this->isDefault = (!empty($matches[self::SASS_DEFAULT]) || !empty($matches[self::SCSS_DEFAULT]));

        // Warn about deprecated features
        if ($matches[self::IDENTIFIER] === self::SASS_IDENTIFIER) {
            $this->addWarning('Variables prefixed with "!" is deprecated; use "' . $this->name . '"');
        }
        if (!empty($matches[SassVariableNode::SASS_ASSIGNMENT])) {
            $this->addWarning('Setting variables with "' . (!empty($matches[SassVariableNode::SASS_DEFAULT]) ? '||' : '') . '=" is deprecated; use "$' . $this->name . ': ' . $this->value . (!empty($matches[SassVariableNode::SASS_DEFAULT]) ? ' !default' : ''));
        }
    }

    /**
     * Parse this node.
     * Sets the variable in the current context.
     * @param SassContext the context in which this node is parsed
     * @return array the parsed node - an empty array
     */
    public function parse($context)
    {
        if (!$this->isDefault || !$context->hasVariable($this->name)) {
            $context->setVariable(
                    $this->name, $this->evaluate($this->value, $context)
            );
        }
        $this->parseChildren($context); // Parse any warnings
        return array();
    }

    /**
     * Returns a value indicating if the token represents this type of node.
     * @param object token
     * @return boolean true if the token represents this type of node, false if not
     */
    public static function isa($token)
    {
        return $token->source[0] === self::SASS_IDENTIFIER || $token->source[0] === self::SCSS_IDENTIFIER;
    }

}